Keto-acid soap greases



Patented Oct. 7, 1 952 UNITED" STATES PATENTYOFFICE inrro acin 80AGREASES Lorne W. Sproule, Warren Pattenden, and

Laurence F. King, Sarnia, Ontario, Canada, as-

signors to Standard Oil Development Company, a corporation of Delaware Ii No Drawing.

Serial No. 137,030

7 Claims, (01. 252-39) The present invention relates to lubricatinggrease compositions and, particularly, to lubricating greases containingsoaps of keto acids of the long chain monocarboxylic'type.""The inven--tion has special application to calciumsoap greases based on such acids,but is not necessarily limited thereto.

Lime soap greases as a class are an important type of lubricants. Theyare widely used in-in dustry because of their smooth texture and theirstructure stability at ordinary temperatures. They are economical andare easily made and for this reason they are used for a majority ofapplications where high temperatures are never encountered. They aresomewhat deficient, however, where temperatures approaching or exceedingthe boiling point of water are encountered, because lime greases relyupon the presence of a small amount of Water to maintain their truecolloidal grease structure. If this water is evaporated, as may occur atmoderately high temperatures, the greases become grainy, the oil separates from the soap, and failure of-lubrication" promptly ensues. i a

It has previously been suggested that lime soap greases might bemodified in various ways toimprove somewhat their high temperatureproperties. Thus, it has been suggested that a compleX soap besubstituted for the conventional soap of straight fatty acids, forexample, by introducing a metal acetate or other low molecular weightwater-soluble salt which forms a complex with the normal fatty acidsoap'and improves high temperature stability. It has also been-suggestedby the present inventors in'a previous application, Serial No. 81,206filed March 12, 1949, that a calcium base grease containing 12-hydroxystearic acid 'might' have improved high temperature properties.

It has now been discoveredthat greases made from keto-acids of the longchain type, for, example, monocarboxylic acids having not less than 12nor more than 22 carbon atoms, have outstanding high temperatureproperties. The

mono-keto-acids are specifically preferred. ,Apj parently, the presenceof the keto group stabilizes lime soap greases in the same manner thatthe presence of a small amount of water stabilizes the conventionalprior art products. The keto group, however, is not afiected by a risingtemperature and the product remains stable where the conventional limebase grease would disintegrate upon evaporation of its normal watercontent. The proportions of soap to be used in such a grease tend to runsomewhat higher than those of conventional lime soaps, but, in general,proportions from 5% to 30% of lime soap, based on the weight of thetotal composition, appear to be operable. Specifically, proportions of10 to about 25% are preferred. The soap may contain other constituentsbut preferably is preponderantly the soap'of one or more of theketo-acids coming within the description given above. Thus; commerciallyavailable products, or products which'can readily be prepared fromconventional rawmaterials may contain other acids such as hydroxy acidsornormal fatty acids along with a major proportion of the keto-a-cidproduct. The keto-stearic acids are particularly suitable, e. g.l2-ketow-stearic acid, ll-:eto-stearic acid, and various other isomers.

The invention may more fully :be understood by reference to the:following specific example:

Example A grease was prepared by heating 20 parts by weight of alz-keto-stearic acid, 20 parts of mineral base lubricating oil, and 2.7parts of hydrated lime. These ingredients were cooked to a temperatureof 250 F; and thereafter additional lubricating oil of mineral base wasadded, together with 1 or 2% of water, until the soap contentapproximated about 22% ofthe weight of,the finished grease. The productthereafter was cooled to about 180 F. and packaged. It showed thefollowing inspection:

Keto-Stearic Acid Grease Soap Content, Percent 22 Worked Penetration 77F Free Acid, Percent Free Alkali, Percent Dropping Point, F

Water Resistance-Percent" Water Absorbed at F.

265 F.nil 150 F.nil. Temperature at which Grease 280 F.trace. F.-traceSeparates 290 F.1% 180 F.-39%.

305 F.l4% .r

1 100 grams of grease are placed in agrease worker. 20 c. c. of wateris'addecl and worked for 300 strokes. If no free water is present, an

from glacial acetic acid, the final product hav- The reaction productwas recrystallized ing an acid number of 186. The product was analyzedand found to contain 89% by weight of 12-keto stearic acid and 11% of12-hydroxy stearic acid.

The table above shows comparisons between the product of the example anda standard commercial lime soap grease of about the same consistency.The soap used in the commercial grease was a mixture of calcium oleateand calcium stearate. It should be noted, as previously indicated, thatthe soap content of keto-stearic acid grease is higher than that of thecommercial product, about 22% of l2-keto stearic acid soap producing agrease of the same consistency as 13% of standard lime soap. In largerbatches, the difference is not quite as great, the soap content beingmore nearly equal, but it appears that somewhat more soap of theketo-acid type is required than of standard fatty acid soaps to producea product of a given consistency.

The product of the example, it will be noted, had a melting or droppingpoint of 290 F., whereas the conventional lime grease melted at 195 F.Both showed excellent water resistance, but at 180 F. the conventionalgrease showed serious oil separation while the keto stearic acid greaseshowed only 1% separation at 290 F. Since oil separation quickly resultsin a failure of the lubricant, it is evident that this is an extremelyimportant consideration where high temperature operation is involved. Inthis respect, greases prepared from l2-keto stearic acid are muchsuperior to conventional lime-stearic acid greases.

While the above example is limited to a particular keto stearic acid, itwill be understood that related products derived from palmitic,myristic, and lauric acids, or from the C20 and C22 fatty acids and thecorresponding. glycerides, may all be used. Mixtures of them may be usedalso, the choice of soap stock depending upon the degree of saturationrequired (which is dependent upon the desired resistance to oxidation,etc.) the softness or hardness of the soap, which is dependent upon thechain length to some extent, and the like as suggested above.Satisfactory soaps have been prepared from 4-keto stearic acid. derivedfrom hydrogenated oiticica oil but various isomers and homologs may beused within the above stated limits.

While lime is the preferred saponifying agent, other metal bases may beused of the alkali metal and alkaline earth metal groups. The greasesalso may contain soaps of other acids, in minor proportions, and theusual modifiers, such as antioxidants, tackiness agents, extremepressure additives, viscosity index improvers, and the like, may beincluded in conventional proportions, as will be evident to thoseskilled in the art.

In general, the products are prepared by combining about 1 to 2 parts ofthe aliphatic monoketo fatty material, which may be either the fattyacid or the corresponding glyceride ester, with 1 to 2 parts by weightof the mineral base lubricating oil. A sufficient quantity of the metalbase saponifying agent is added to saponify and substantially neutralizethe fatty material. These ingredients are heated to saponificationtemperature between about 200 and 300 F. Thereafter, further quantitiesof oil are added, from 2 to 10 parts by weight, depending upon theconsistency desired in the finished product. This additional oil ispreferably a mineral base oil, but synthetic oils, such as theconventional dibasic acid alkyl esters or the polyglycols, or mixturesthereof, with each other and/or With mineral base oil, may be employed.As is well-known in the art, the esters are not very suitable forforming the original soap in situ, and when an ester base grease isdesired the soap should be preformed independently or should b formed inmineral oil which does not hydrolyze during the saponification.

Soaps of the keto-acids may be preformed in much the same manner asconventional soaps and by the use of suitable homogenizing equipmentthese may be incorporated into lubricating oils, like other preformedsoaps, to prepare the greases. The formation of the soap in situ, asdescribed in detail above, is usually preferred.

What is claimed is:

1. A lubricating grease composition comprising a major proportion oflubricating oil thickened to a grease consistency with a minorproportion of a metal soap of 12-keto stearic acid.

2. A lubricating grease composition comprising a mineral baselubricating oil thickened to grease I consistency with a soap of a metalselected from the alkali and alkaline earth metals, said soap beingpredominantly of lz-keto stearic acid.

3. Composition according to claim 2 wherein the metal soap is a limesoap. 1

4. Composition according to claim 1 wherein the metal soap is a limesoap.

5. The process of preparing a lubricating grease which comprisescombining about 20 parts by weight of mineral base lubricating oil,about 20 parts of an aliphatic monocarboxylic acid which ispredominantly 12-keto stearic acid, and about 2.7 parts of hydratedlime, heating the mixture to a temperature of about 250 F. for a timesulficient to substantially complete saponification to form a greasethickening soap, and thereafter adding additional lubricating oil andcooling to form a grease of 5 to 30% soap content by weight.

6. A lubricating grease composition consisting essentially of mineralbase lubricating oil thickened to a grease consistency with 5 to 30% byweight, based on the total composition, of the lime soap of an acidcomposed substantially of 11% by weight of 12-hydroxy stearic acid and89% 12-keto stearic acid.

7. Composition according to claim 6 having asoap content of about 22% byweight.

LORNE W. SPROULE. WARREN C. PATTENDEN. LAURENCE F. KING.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OFLUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH A MINORPROPORTION OF A METAL SOAP OF 12-KETO STEARIC ACID.